The present invention relates to a screwdriver for introducing and screwing a screw into the human or animal body and/or for unscrewing and removing a screw from the human body.
A screwdriver of this kind for medical purposes is known from DE 35 39 502 C1.
In the area of medical surgery, screwdrivers are used to screw bond screws into bones in the human or animal body and to remove them again. The problem frequently arises in this context that the surgical field into which the screw is to be introduced is difficult to access from outside, so that it is not possible to bring the screw to the target location by hand and hold it there so the screw can then be accurately and securely screwed in, unless a large opening in the body is created for that purpose in order to expose the surgical field, or a second incision is created into which an instrument for guiding and holding the screw can be introduced.
One special application in surgery is laparoscopic spinal column surgery, in which a bone screw, or several bond screws in succession, is or are brought through the abdominal cavity through a surgical opening in the abdominal wall to the spinal column and screwed into the latter. A screwdriver having a correspondingly elongated shaft is necessary for this procedure. Since it is desirable to perform such an operation in minimally invasive fashion, i.e. from outside through the smallest possible incision in the abdominal wall, there exists a need for a screwdriver with which the screw can not only be screwed in, but also first reliably introduced through the abdominal cavity to the spinal column without having the screw fall off the screwdriver during insertion. The screw must also be capable of being held by the screwdriver so securely that at the target location at which the screw is to be screwed in, it can be put in place without tilting to the side when pressure is exerted on the screw. It should moreover be possible, in one working step, not only to set the screw in place but also to screw it completely into the bone, without having the retention device interfere with complete insertion of the screw.
The screwdriver known from the aforementioned DE 35 39 502 C1 for introducing and screwing in a bone screw has a handle as well as a shaft whose front end has a head which can be brought into engagement with a screw head of the screw in order to screw in and unscrew the screw. The screwdriver furthermore has a retention device for retaining the screw on the shaft, the retention device having an inner tubular shaft which surrounds the shaft and has at the front end a clamping gripper preloaded into its open position, and an outer tubular shaft surrounding the inner tubular shaft. The screwdriver furthermore has an actuation device for the inner tubular shaft and outer tubular shaft which can be moved from a first position into a second position, thereby displacing the clamping gripper over the head from a pulled-back position, the actuation device being movable from the second position into a third position which causes the outer tubular shaft to be displaced relative to the inner tubular shaft over the clamping gripper in order to close the latter, and vice versa. The longitudinal movement of the outer tubular shaft with respect to the inner tubular shaft is limited in each case, in the direction away from the tool, by stops.
With this known screwdriver, the inner tubular shaft, the outer tubular shaft, and the shaft itself can be removed from the handle, for which purpose a coupling is provided between the tool shaft and the handle. The fact that the known screwdriver can be disassembled means that the screwdriver can be sterilized, so that the known screwdriver also meets the requirements for easy cleaning that always apply to medical instruments.
It is, however, disadvantageous in terms of the design and handling capabilities of this known screwdriver that in order to remove the tool shaft, an actuation device separate from the actuation device for the retention device is provided. This second actuation device for disassembling the instrument comprises a sliding sleeve that is arranged between the handle and the actuation device for the retention device. The handling of the known screwdriver is complicated by the fact that because of the actuation device for disassembling the instrument, the actuation device for the retention device is located far away, thus making one-hand handling impossible or at least difficult.
DE 38 4 749 A1 furthermore discloses a screwdriver having a retention device for bone screws. With this screwdriver, no mention is made of the possibility for disassembly into handle and shaft parts.
CH Patent 369 416 also discloses a screwdriver having a gripper for retaining a screw, in which the gripper sleeve, slid onto the screwdriver loosely on the shaft, possesses inwardly protruding holding means, engaging the former and imparting a flexible braking effect, in such a way that the gripper sleeve, when displaced, automatically holds itself on the screwdriver shaft and, to allow disassembly of the latter, the gripper sleeve can be completely pulled off the screwdriver shaft as a result of its loose arrangement. With this known screwdriver, the retention device therefore cannot be immobilized on the handle.
U.S. Pat. No. 2,370,407 discloses a screwdriver having a retention device for a screw that also has an inner tubular shaft with a clamping gripper and an outer tubular shaft which can be displaced axially on the inner tubular shaft in order to close and open the clamping gripper. A nut that is immovably joined to the outer tubular shaft and is in threaded engagement with the inner tubular shaft is provided as an actuation device for displacing the outer shaft relative to the inner tubular shaft. The inner tubular shaft and outer tubular shaft are not immobilized on the handle while the screwdriver is in operation.
Lastly, DE 37 14 994 C1 discloses a screwdriver having a screw holding apparatus, in which the screw holding apparatus can be screwed as a part onto threads on the shaft of a screwdriver. For that purpose, the screw holding apparatus comprises a retaining jaw sleeve on which the sleeve of a detent bushing sleeve is arranged. The detent bushing, which can be screwed onto the sleeve, is rotatably joined to an adjusting screw. For assembly, firstly the retaining jaw sleeve is inserted from one side into a slide bushing while compressing the detent tooth clamps, once the sleeve has previously been slid on. The detent bushing is then introduced into the slide bushing from the other side, and is thread-joined to the sleeve. With this known screwdriver, the disassembly capability is achieved with a complex design. Handling in order to disassemble and assemble the screwdriver is also complicated.
It is therefore one object of the present invention to develop a screwdriver of the kind cited initially in such a way that, with a configuration of simple design, both actuation of the retention device and disassembly and assembly of the screwdriver are easy.